sine_screensaver.pde

float i = 0;
int verticalLines = 54;
float waveHeight = 100;
float colorChange = 1;
float colorSpeed = 3;

boolean mouse = false;

public void setup() {
  smooth();
  fullScreen();
  
  strokeWeight(5);
  colorMode(HSB, 100);
  
  waveHeight = height / 5;
  noCursor();
}

void draw() {
  pushMatrix();
  translate(0, height / 2);
  
  background(0);
  float sinDivider = 30;
  for(int n = 0; n < verticalLines; n += 2) {
    stroke((i * colorSpeed + n * colorChange) % 100, 100, 100);
    float y1 = (sin((i + n * 2) / sinDivider * TWO_PI) + 1) * waveHeight;
    line(n * width / verticalLines, y1, (n + 1) * width / verticalLines, y1);
    float y2 = (sin(((i + n * 2) / sinDivider + 0.5) * TWO_PI) + 1) * waveHeight * -1;
    line((n + 1) * width / verticalLines, y1, (n + 1) * width / verticalLines, y2);
    line((n + 1) * width / verticalLines, y2, (n + 2) * width / verticalLines, y2);
    y1 = (sin((i + (n + 2) * 2) / sinDivider * TWO_PI) + 1) * waveHeight;
    line((n + 2) * width / verticalLines, y2, (n + 2) * width / verticalLines, y1);
  }
  
  popMatrix();
  i = i + 0.3;
}

void mouseMoved() {
  if (mouse) {
    exit();
  } else {
    mouse = true;
  }
}

(Sry at school so I can't comment on scratch)

Tbh i don't know why this happens, it might be a windows or java bug. I tried making a screensaver myself once and it also didn't work properly :L

i'll look into it though